Nowadays, humans are increasingly exposed to different types of stress. In addition, human population is getting older every day. Those are only few of the factors involved in the increased number of tumour patients all over the world. Due to the increased number of tumour patients, as well as due to the relatively low efficacy of the current tumour treatments, there is a growing need for a more efficient tumour treatment, i.e., more efficient anti-tumour agent to be used in said treatments. Most tumours belong to the group of the so called solid tumours, such as breast tumour, ovary tumour, prostate gland tumour, lung tumour etc., while leukemia and lymphomas belong to the group of hematological tumours. Successful treatment of tumour patients has not yet been achieved—every third patient dies of said disease. Therefore, enormous efforts have been invested in the development of new, more successful types of tumour treatment.
Chemotherapy is the method of choice in tumour treatment. In classical chemotherapy, which is still the most used treatment, drugs with a stronger effect on dividing cells (where cell division is one of the main characteristics of tumour cells) are used. The particular problem of this type of treatment is the development of tumour cell resistance. Thereupon, tumour cells use maximally all molecular protective mechanisms (that are active in normal cells) to protect themselves from the treatment. Due to selective pressure caused by chemotherapy, the number of resistant tumour cells increases, which finally leads to insufficient efficiency of classical cytostatics in tumour treatment. Thus, insufficient efficiency of the existing tumour treatments raises the need for new, more effective compounds, as well as for the new strategies of tumour treatment.
Publications disclosing the efficiency of compounds having triazene group are being published from 1980 until present. They are mainly related to the group of alkylating agents having similar chemical, physical, anti-tumour and mutagenic characteristics: dacarbazine, procarbazine, mitozolomide, and the newest temozolomide. Some of the above said alkylating agents are already used in clinical practise (Serrone et al., J Exp Clin Cancer Res 19(2000)21; Advani et al., J Natl Comp Canc Netw 4(2006)241; Cassier et al., Expert Opin Emerg Drugs 12(2007)139; Brandsma et al., Curr Opin Oncol 19(2007)598; Quirbt et al., Curr Oncol 14(2007)27). Mechanism of their action is mainly based on methylation of the 06 position of guanine in the DNA. These adducts cause mismatched bases that can finally lead to cell death or, if cells survive, to somatic mutations. Unfortunately, during the tumour therapy, cell resistance to said compounds, based on increased level/activity of enzyme O6-alkylguanine-DNA-alkyl transferase, is developed (Marchesi i sur., Pharmacol Res 56(2007)275).
Another known compound having three nitrogen atoms in its structure is Berenil (Brown et al., EMBO J 9(1990)1329). This triazene has two protonated amidine NH2 groups (electron acceptors, which as a part of the larger C(NH2)2+ group act as electron-withdrawing groups). Berenil binds into the minor groove of DNA molecules (Pilch et al., Biochem 34(1995)9962) thus inhibiting the processes linked to DNA: from cell division to gene transcription. The published results showed its toxicity to tropical parasites from the genera Trypanosoma and Leischmania (Olliaro et al., Expert Opin Emerg Drugs 7(2002)61). There is only one publication in which the cytotoxicity of berenil was examined on mammalian cells. Said compound showed very low activity (IC50>100 μM). However, by binding to chromophore acridine, which intercalates in DNA, its activity was significantly increased (Mc Connaughie and Jenkins, J Med Chem 38(1995)3488).
Patent GB 893 437 describes therapeutic compositions comprising substituted triazenes, which are used for tumour treatment. Therefore, the compounds used in accordance with this patent have triazene-based structure. Said compounds show selective activity for adenocarcinoma in mammals (72j). Some of described compounds also contain two phenyl groups having different substituent. However, none of the mentioned compounds have nitro substituent on both phenyl groups.
U.S. Pat. No. 4,923,970 describes the new substituted 1-(2-chloroethyl)-3-acyl-3-alkyl-triazenes and the method of their synthesis. Said compounds bind to DNA and induce its cross-linking causing cell death. The compounds of the above mentioned patent are not bis-substituted triazenes and have chloroethyl group on nitrogen atom of triazene. Considering that all compounds disclosed with the present invention are bis-substituted compounds, and none of them has the chloroethyl group on the nitrogen atom, the compounds of the present invention differ from the compounds as described in the above mentioned patent.
U.S. Pat. No. 3,976,633 describes bis-substituted cyano-trifluoromethylphenyl triazenes which help the regulation of body weight. Even though the compounds of this patent have triazene-based structure, their substituent groups differ from the substituent groups of the present invention, meaning that the compounds are, thus, not similar. In addition, this patent refers to compounds effective in the regulation of body weight, which is not the subject-matter of the present invention.
U.S. Pat. No. 3,299,038 describes carboxamide 3-triazenes showing anti-inflammatory effect and the method of their synthesis. One of the starting compounds used for the synthesis of such compounds is 1,3-bis-(4-nitrophenyl)triazene. Given that this compound is only the starting substance for the synthesis of the compounds protected by this patent, its role in the present invention is only of chemical nature.
U.S. Pat. No. 3,932,633 describes o-triazenobenzamides and their application in the prevention and treatment of aggressive behaviour of patients. The compounds have benzamide group that does not appear as substituent in the present invention. Therefore, these compounds differ from the compounds disclosed in the present invention.
U.S. Pat. No. 3,907,767 describes 1-phenyl-3-hydroxy-3-methyltriazenes and the method of their synthesis. The compounds contain only one phenyl group, differing, thus, from the compounds referred to in the present invention.
The treatment of tumours is usually based on combination of different medical interventions such as surgical elimination of the tumour, chemotherapy or radiation. In chemotherapy chemical substances of natural or synthetic origin are used for systemic tumour treatment and tumour cell division is controlled chemically. Most cytostatics used in classical chemotherapy damage DNA by disturbing its synthesis and/or function, having death of tumour cells as a result.
One of the limiting factors in the tumour treatment with cytostatics is the development of tumour cell resistance. Drug resistance is mostly caused by genetic instability of tumour cells and their increased capacity to adapt to unfavourable growth conditions, such as therapy, and to activate different molecular mechanisms to develop resistance. Acquired drug resistance during chemotherapy is well known for standard cytostatics such as cisplatin, doxorubicin etc. In addition to developed resistance to the cytostatic used for treating the tumour, a cross-resistance to other cytostatics, which are completely different by structure and activity, is usually developed. Therefore, tumour cells resistant to cisplatin may become cross-resistant to carboplatin, doxorubicin, melphalan, methotrexate etc. To which additional compounds cross-resistance will be developed depends on the cytostatic itself, its administration route, as well as on the tumour cell type and status.
In order to inhibit the development of tumour cell resistance to cytostatics, a combination of several (usually 2-3) cytostatics, which kill tumour cells by different mechanisms, is used nowadays.
Due to development of cross-resistance to classical cytostatics, new compounds that target tumour cells through different mechanisms would be most welcome. The use of combination of classical cytostatics with new compounds in tumour therapy would reduce cross-resistance development.